Effects of Thickness Ratio of Co to Pt Layer on Magnetic Properties and Microstructure of [Co/Pt]<sub><italic>n</italic></sub> Multilayer Films

Abstract

[Co/Pt] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> multilayer films were deposited on a glass substrate with a Pt underlayer by an alternative sputtering method. The effect of overall multilayer [CoPt]n thickness and the relative thickness of Co to Pt layers on the structural and magnetic properties were investigated. First, the thickness ratio of Co to Pt layers (Co:Pt = 4:3, 1:1, and 3:4) in [Co/Pt]n multilayer films was varied. Higher coercivity and out-of-plane squareness were found for the [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1 nm</sub> /Pt <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75 nm</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> and [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1 nm</sub> /P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t1 nm</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> multilayer films. The total thickness of multilayers was varied from 3.5 to 8 nm. When the Co to Pt layers thickness ratio was changed to 3:4, the magnetic performance was declined. Furthermore, the thickness ratio of Co to Pt layers was kept constant to 1:1, and the Co and Pt layer thickness in [C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox nm</sub> /P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tx nm</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> film was varied. The highest coercivity of 2.1 kOe was obtained in the [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> /Pt <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> film. The magnetic properties were decreased with further increase in the Co and Pt layer thickness. In this paper, we demonstrated that [Co/Pt]n multilayer films with the suitable thickness ratio of Co to Pt layers are beneficial to prepare CoPt thin films with perpendicular magnetic anisotropy.